The aim of this project is to examine the cellular mechanisms responsible for the transmission of sensory information at afferent synapses in the dorsal horn of the spinal cord. Several classes of cutaneous afferent fibres have been defined physiologically and morphologically but the transmitters released from individual subclasses of sensory neurons are unknown. Biochemical, cytochemical and immunological techniques will be used to identify specific chemical markers for subpopulations of dorsal root ganglion (DRG) neurons. These markers will be used to correlate chemical and functional properties of DRG neurons and to provide information on the transmitters released by sensory neurons. The physiological action of potential sensory transmitters, will be examined by intracellular recording from dorsal horn neurons grown in dissociated cell culture. Co-cultures of DRG and dorsal horn neurons will be used to compare the response of dorsal horn neurons to sensory synaptic input and transmitter candidates. Attention will be focused on a class of DRG neurons that contain a 5'-nucleotide hydrolysing enzyme and the possibility that these, and perhaps other, DRG neurons release ATP as an excitatory transmitter. A subpopulation of dorsal horn neurons are selectively and potently excited by ATP and indirect evidence suggests that ATP may be a sensory transmitter. This possibility will be investigated using biochemical, immunological and physiological techniques. To provide new information on the properties of sensory afferents, monoclonal antibodies will be generated against both defined and novel antigens expressed on the surface and in the cytoplasm of DRG neurons. Defined antigens include the 5'-nucleotide hydrolysing enzyme and the ATP binding site. Somatic cell hybridization techniques will be used to generate hybrid cell lines that express differentiated properties of DRG neurons and provide large amounts of material for biochemical and immunological studies. These studies are intended to improve understanding of the way in which information is processed in the spinal cord.